Kidney Failure, Acute

Your kidneys are like tiny filters for your blood. They remove extra water and waste products. These filters are called nephrons, and each nephron has a special part called a glomerulus. The glomerulus is like a tiny sieve made of very small blood vessels (capillaries). When blood flows through the glomerulus, small bits of water, minerals, nutrients, and waste products easily pass through the walls of the capillaries. Larger things, like proteins and red blood cells, stay behind.

This filtered material then moves into another part of the nephron called a tubule. Your body reabsorbs the water, nutrients, and minerals it needs back into the bloodstream. The extra water and waste products become urine, which travels to your bladder.

Acute kidney injury (AKI) happens when your kidneys suddenly can't filter waste properly. This means harmful waste products can build up in your blood, and your blood's balance of chemicals can become disrupted. Previously, this was called acute kidney failure.

AKI is more common in hospitalized patients, especially those in intensive care. It can range from mild to severe. If AKI is severe, untreated, and ongoing, it can be life-threatening. However, it's often possible to treat it successfully. People who are generally healthy often recover and regain normal or near-normal kidney function.

Acute kidney injury can have various signs and symptoms, but sometimes it has none at all. When symptoms are present, they might include:

• Reduced urination: You may produce less urine than usual.
• Fluid buildup: Extra fluid can collect in your body, leading to swelling in your legs, ankles, or feet. This extra fluid can also make it hard to breathe.
• Feeling tired: You might experience general fatigue or weakness.
• Mental confusion: You could feel disoriented or have trouble concentrating.
• Upset stomach: Nausea and vomiting are possible symptoms.
• Belly or side pain: Some people experience pain in their abdomen or the area below their ribs.
• General weakness: Feeling weak or having trouble moving around.
• Heart rhythm problems: Your heart might beat irregularly.
• Itching: Skin itching can be a sign.
• Loss of appetite: You may not feel hungry.
• Serious complications: In severe cases, acute kidney injury can lead to seizures or a coma.

Importantly, acute kidney injury can sometimes occur without any noticeable symptoms. In these cases, it might only be detected during routine medical tests that are done for other reasons.

If you think you might have acute kidney injury, see a doctor or go to the emergency room immediately.

Acute kidney injury (AKI) occurs when the kidneys stop working properly. This can happen in several ways:

1. Reduced Blood Flow to the Kidneys: If blood flow to the kidneys slows down, they can't filter waste and excess fluid as effectively. This can be caused by:

• Dehydration: Losing too much body fluid reduces the blood volume, slowing the flow to the kidneys.
• Infections: Infections, sometimes with severe complications like sepsis or septic shock, can also restrict blood flow to vital organs, including the kidneys.
• Medications: Certain pain relievers like aspirin, ibuprofen, and naproxen can harm the kidneys if taken in excessive amounts or for prolonged periods.
• Blood loss: Significant blood loss from injuries or other causes can decrease blood volume, affecting kidney function.
• Heart problems: Heart attack, heart failure, and heart disease can reduce blood flow throughout the body, including to the kidneys.
• Liver problems: Cirrhosis or liver failure can affect the body's ability to filter waste products, putting stress on the kidneys.
• Severe allergic reactions (anaphylaxis): This can cause a sudden drop in blood pressure, reducing blood flow to the kidneys.
• Severe burns: Extensive burns can trigger a cascade of effects, including reduced blood flow and kidney damage.

2. Direct Kidney Damage: Sometimes, the kidneys themselves are directly harmed, leading to AKI. This can result from:

• Inflammation: Conditions like glomerulonephritis involve inflammation of the tiny filtering units (glomeruli) in the kidneys.
• Medications: Certain chemotherapy drugs, antibiotics, and dyes used for imaging tests can damage the kidneys.
• Infections: Infections, such as COVID-19, can directly harm the kidneys.
• Toxins: Exposure to toxins like alcohol, heavy metals, and cocaine can severely damage kidney function.
• Autoimmune diseases: Conditions like lupus can cause inflammation and damage the kidneys.
• Blood clots: Blood clots in the blood vessels around the kidneys can restrict blood flow and cause damage.
• Cholesterol buildup: Cholesterol deposits can block blood vessels in the kidneys, reducing blood flow.
• Hemolytic uremic syndrome (HUS): This condition involves the premature destruction of red blood cells, leading to kidney damage.
• Scleroderma: This rare group of diseases affects the skin and connective tissues, and can also impact the kidneys.
• Thrombotic thrombocytopenic purpura (TTP): A rare blood disorder that can cause blood clots and harm the kidneys.
• Muscle breakdown (rhabdomyolysis): Damaged muscle releases toxins that can harm the kidneys.
• Tumor lysis syndrome: The breakdown of cancer cells can release toxins that are harmful to the kidneys.

3. Blockage of Urine Drainage: When urine can't flow out of the body, it can build up and damage the kidneys. This is called urinary obstruction. Possible causes include:

• Kidney stones: Hard deposits in the kidneys can block the flow of urine.
• Enlarged prostate: An enlarged prostate gland can press on the urethra, blocking urine flow.
• Blood clots: Blood clots in the urinary tract can obstruct urine flow.
• Cancer: Cancers in the bladder, prostate, cervix, or colon can put pressure on the urinary system, leading to blockages.
• Other growths: Tumors or growths pressing on the ureters (tubes carrying urine from the kidneys to the bladder) can cause obstruction.
• Nerve damage affecting the bladder: Nerve damage can interfere with bladder control, leading to urinary retention and potential kidney damage.

Understanding the causes of AKI is crucial for early diagnosis and treatment. If you experience symptoms like decreased urine output, swelling, or fatigue, it's essential to seek medical attention promptly.

Acute kidney injury (AKI) is often a symptom of another health problem. Many things can raise your chances of getting AKI. These include:

• Pre-existing kidney disease (chronic kidney disease): If your kidneys are already struggling, they're more vulnerable to further damage.

• Age: While AKI can affect people of any age, older adults are at higher risk. It's important to remember that children can also develop AKI.

• Hospital stays: Being hospitalized, especially for serious illnesses requiring intensive care, increases the risk. This is because of the stress on the body and the use of certain medications.

• Blood vessel problems (peripheral artery disease): Blockages in the blood vessels of your arms or legs can reduce blood flow to the kidneys, putting them at risk.

• Diabetes: Uncontrolled diabetes can harm blood vessels and the kidneys. The effect is worse the less controlled the diabetes is.

• Heart failure: When the heart can't pump blood efficiently, the kidneys don't receive enough blood, increasing their risk of injury.

• Liver diseases: Issues with the liver can sometimes affect the kidneys.

• Cancer and its treatments: Certain types of cancer and their treatments can put stress on the kidneys and lead to AKI. This is often due to the treatments and the illness itself.

Acute kidney injury can lead to several serious problems.

• Fluid buildup: Extra fluid can collect in your lungs, making it hard to breathe. This is called fluid overload.

• Chest pain: The lining around your heart (pericardium) might become inflamed. This inflammation can cause chest discomfort.

• Muscle weakness: When the balance of salts and minerals (electrolytes) in your blood is disrupted, it can cause muscle weakness. These electrolytes are crucial for many bodily functions.

• Long-term kidney damage: Sometimes, acute kidney injury leads to permanent kidney damage. This is known as end-stage renal disease (ESRD). People with ESRD need ongoing treatments to remove waste products from their blood, like dialysis, or a kidney transplant to survive.

• Loss of life: If acute kidney injury isn't treated, it can cause the kidneys to stop working completely, which can be fatal.

Taking good care of your kidneys can help lower your chances of getting acute kidney injury. Here's how:

• Treat infections promptly: If you have an infection, getting it treated quickly is important. This helps prevent the infection from spreading and potentially damaging your kidneys. Prompt treatment means seeing a doctor as soon as possible.

• Maintain a healthy lifestyle: A healthy lifestyle is key for overall well-being, and this includes your kidneys. Regular physical activity, like walking or swimming, is beneficial. Focus on a balanced diet rich in fruits, vegetables, and whole grains. If you choose to drink alcohol, do so in moderation. Excessive alcohol consumption can harm your kidneys.

• Talk to your doctor about medications: If you have conditions that put you at risk for kidney problems, talk to your healthcare provider. They can help you understand if any prescription medicines you are taking might be hard on your kidneys. They can advise you on the safest and best options for your health. This is especially important if you have a history of kidney disease in your family or other risk factors. Your doctor can assess your individual needs and recommend adjustments to your treatment plan if necessary.

A kidney biopsy is a procedure where a healthcare professional takes a tiny piece of kidney tissue to be examined in a lab. They use a needle to carefully remove the sample, often guided by an imaging device like an ultrasound machine. This helps them see the kidney and precisely place the needle.

To figure out what's causing kidney problems, doctors might use several tests:

• Blood tests: These check the levels of urea and creatinine in your blood. These substances are normally filtered out by healthy kidneys. If your kidneys aren't working well, the levels of these substances will likely be higher than usual. This gives doctors an idea of how well your kidneys are functioning.

• Urine output: Measuring how much urine you produce over 24 hours can help determine if your kidneys are filtering waste properly. Changes in urine output can point to different potential problems.

• Urine tests (urinalysis): Examining a urine sample can reveal signs of infections, substances that shouldn't be present, or other abnormalities that could indicate a kidney issue.

• Imaging tests: Ultrasound and CT scans are helpful tools for visualizing the kidneys. They provide detailed pictures of the kidney's structure, allowing doctors to identify any physical abnormalities.

• Kidney biopsy: In some cases, a kidney biopsy might be needed. This involves removing a tiny piece of kidney tissue with a needle inserted through the skin directly into the kidney. This tissue sample is then sent to a lab for detailed analysis. This can help doctors pinpoint the exact cause of kidney problems, if other tests don't provide a clear answer.

Acute kidney injury (AKI) usually requires a hospital stay. Most people needing treatment for AKI are already hospitalized. How long you stay depends on what caused the injury and how quickly your kidneys recover.

The first step in treating AKI is to figure out what caused the problem. This might be an illness, an injury, or even a medicine you're taking. Treatment will depend on the specific cause. For example, if a medication is harming the kidneys, stopping that medication might be part of the treatment plan.

The goal of treatment is to prevent further complications and give the kidneys time to heal. Here are some common treatments:

Managing Fluid Balance:

If your AKI is caused by not having enough fluids in your blood, you might receive fluids directly into your veins (intravenous fluids, or IV fluids).

Conversely, if your AKI leads to too much fluid in your body, causing swelling in your arms and legs, you might be given medicines called diuretics. These help your body get rid of extra fluid.

Removing Harmful Substances:

If waste products build up in your blood, you might need a procedure called hemodialysis (or just dialysis). Dialysis acts like an extra kidney, removing harmful waste and excess fluid from your blood while your kidneys recover. It can also help remove extra potassium. During dialysis, a machine filters your blood, removing the toxins, and then returns the cleaned blood to your body.

Managing Potassium Levels:

High levels of potassium in the blood can be dangerous, causing irregular heartbeats (arrhythmias) and muscle weakness. If this is a concern, you might be given medicines called potassium binders. These medications help prevent potassium from building up in your blood. Examples of these medicines include sodium zirconium cyclosilicate (Lokelma) and patiromer (Veltassa).

After an acute kidney injury, your body needs special care to recover. A dietitian can help you with a diet that's gentle on your kidneys, reducing the extra work they have to do.

Your dietitian will likely recommend some changes to your eating habits. These changes are designed to help your kidneys heal.

• Limit potassium-rich foods: Some foods have a lot of potassium, a mineral important for your body, but too much can be hard on your kidneys. Good choices include apples, peaches, carrots, green beans, white bread, and white rice. Foods to limit or avoid include potatoes, bananas, tomatoes, oranges, beans, and nuts.

• Cut back on salt: Many processed foods and drinks contain added salt. This includes frozen meals, canned soups, fast food, salty snacks, canned vegetables, and processed meats and cheeses. Try to eat less of these.

• Control phosphorus: Phosphorus is another mineral found in some foods. Too much phosphorus in your blood can be harmful, potentially weakening your bones and causing skin itching. Be mindful of foods like dark-colored sodas, milk, oatmeal, and bran cereals. Your dietitian can give specific recommendations for how much to eat.

As your kidneys get stronger, you might not need this special diet anymore. However, even after recovery, maintaining a healthy diet is essential for overall well-being.